Polishing apparatus having thermal energy measuring means

ABSTRACT

A polishing apparatus is used for polishing a substrate such as a semiconductor wafer to a flat mirror finish. The polishing apparatus includes a polishing table having a polishing surface, a substrate holding apparatus configured to hold the substrate and to press the substrate against the polishing surface, and a controller. The substrate holding apparatus includes an elastic membrane configured to form a substrate holding surface which is brought into contact with the substrate, a carrier provided above the elastic membrane, at least one pressure chamber formed between the elastic membrane and the carrier, and an infrared light detector configured to measure thermal energy from the elastic membrane. The controller calculates an estimate value of a temperature of the elastic membrane using a measured value of the infrared light detector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing apparatus and method, andmore particularly to a polishing apparatus and method for polishing anobject to be polished (substrate) such as a semiconductor wafer to aflat mirror finish.

2. Description of the Related Art

In recent years, high integration and high density in semiconductordevice demands smaller and smaller wiring patterns or interconnectionsand also more and more interconnection layers. Multilayerinterconnections in smaller circuits result in greater steps whichreflect surface irregularities on lower interconnection layers. Anincrease in the number of interconnection layers makes film coatingperformance (step coverage) poor over stepped configurations of thinfilms. Therefore, better multilayer interconnections need to have theimproved step coverage and proper surface planarization. Further, sincethe depth of focus of a photolithographic optical system is smaller withminiaturization of a photolithographic process, a surface of thesemiconductor device needs to be planarized such that irregular steps onthe surface of the semiconductor device will fall within the depth offocus.

Thus, in a manufacturing process of a semiconductor device, itincreasingly becomes important to planarize a surface of thesemiconductor device. One of the most important planarizing technologiesis chemical mechanical polishing (CMP). Thus, there has been employed achemical mechanical polishing apparatus for planarizing a surface of asemiconductor wafer. In the chemical mechanical polishing apparatus,while a polishing liquid containing abrasive particles such as silica(SiO₂) therein is supplied onto a polishing surface such as a polishingpad, a substrate such as a semiconductor wafer is brought into slidingcontact with the polishing surface, so that the substrate is polished.

This type of polishing apparatus includes a polishing table having apolishing surface formed by a polishing pad, and a substrate holdingdevice, which is referred to as a top ring or a polishing head, forholding a substrate such as a semiconductor wafer. When a semiconductorwafer is polished with such a polishing apparatus, the semiconductorwafer is held and pressed against the polishing surface under apredetermined pressure by the substrate holding device. At this time,the polishing table and the substrate holding device are moved relativeto each other to bring the semiconductor wafer into sliding contact withthe polishing surface, so that the surface of the semiconductor wafer ispolished to a flat mirror finish.

In such polishing apparatus, if the relative pressing force appliedbetween the semiconductor wafer, being polished, and the polishingsurface of the polishing pad is not uniform over the entire surface ofthe semiconductor wafer, then the surface of the semiconductor wafer ispolished insufficiently or excessively in different regions thereof,which depends on the pressing force applied thereto. It has beencustomary to uniformize the pressing force applied to the semiconductorwafer by providing a pressure chamber formed by an elastic membrane atthe lower portion of the substrate holding device and supplying thepressure chamber with a fluid such as compressed air to press thesemiconductor wafer against the polishing surface of the polishing padunder a fluid pressure through the elastic membrane.

On the other hand, a thin film formed on a surface of a semiconductorwafer as an object to be polished has different thicknesses depending onradial locations of the semiconductor wafer due to characteristics of afilm-forming method or apparatus. Specifically, the thin film formed onthe surface of the semiconductor wafer has an initial film thicknessdistribution in its radial direction. Therefore, as described above, inthe substrate holding device for pressing the entire surface of thesemiconductor wafer uniformly and polishing the semiconductor wafer, thesemiconductor wafer is polished uniformly over the entire surfacethereof, and thus the above initial film thickness distribution on thesurface of the semiconductor wafer cannot be corrected. Therefore, asdisclosed in Japanese laid-open patent publication No. 2006-128582,there has been proposed a polishing apparatus in which a plurality ofpressure chambers are formed by an elastic membrane within a surface ofthe semiconductor wafer, and pressures of a pressurized fluid such ascompressed air to be supplied to the respective pressure chambers areindependently controlled to control pressures applied to thesemiconductor wafer at the respective areas on the semiconductor wafer.Therefore, in such a polishing apparatus, a pressing force for pressingthe semiconductor wafer against the polishing surface is made larger atthe area having a thick film than that at the area having a thin film,and the polishing rate of the area having the thick film is selectivelyenhanced to polish the semiconductor wafer flatly over the entiresurface of the semiconductor wafer without relying on the film thicknessdistribution at the time of film-forming.

When a substrate such as a semiconductor wafer is polished by thepolishing apparatus having the above structure, the substrate is pressedagainst the polishing surface of the polishing pad under a certainpolishing pressure and is brought into sliding contact with thepolishing surface. As a result, a temperature of contact surface of thesubstrate with the polishing pad, i.e., a polishing temperature israised. As described above, it is important to control the polishingpressure for the purpose of improving polishing performance. However, itis also very important to measure and control the polishing temperaturefor the purpose of improving the polishing performance. Specifically,because the polishing pad is composed of a resin material such as foamedpolyurethane, the polishing temperature changes rigidity of thepolishing pad to have an influence on planarization characteristic ofthe substrate. Further, since the chemical mechanical polishing (CMP) isa polishing method which utilizes a chemical reaction between apolishing liquid (polishing slurry) and a surface, being polished, ofthe substrate, the polishing temperature has an influence on chemicalcharacteristic of the polishing slurry. Further, the distribution of thepolishing rate changes depending on the polishing temperature todeteriorate the yield rate or to lower the polishing rate, thusdeteriorating productivity of the polishing apparatus. Further, if thereis temperature distribution within the surface of the substrate, thepolishing performance within the surface of the substrate becomesnonuniform.

Therefore, as disclosed in Japanese laid-open patent publication Nos.2002-301660 and 2005-268566, a temperature of a substrate such asemiconductor wafer is measured during polishing. Further, as disclosedin Japanese laid-open patent publication No. 2006-332520, a temperatureof a membrane for holding a semiconductor wafer is measured as a meansfor measuring a temperature of a portion near a surface, being polished,of the semiconductor wafer during polishing.

SUMMARY OF THE INVENTION

As described above, in Japanese laid-open patent publication Nos.2002-301660, 2005-268566 and 2006-332520, the temperature of thesubstrate such as a semiconductor wafer or the temperature of themembrane for holding the semiconductor wafer is measured duringpolishing. Further, Japanese laid-open patent publication No.2002-301660 discloses that in order to measure a temperature of asubstrate with high accuracy, the temperature of the surface of thesubstrate is measured by detecting infrared lights of two or morewavelengths from a reverse side of the substrate. However, in thetechnology disclosed in Japanese laid-open patent publication No.2002-301660, as a method of pressing the substrate, a membrane forforming a pressure chamber cannot be used, and thus uniform distributionof the polishing rate cannot be obtained. Further, since the temperatureof the surface, being polished, of the substrate is measured bymeasuring the infrared light which has passed through the substrate,transmission condition of the infrared light differs depending on thekind of film on the substrate, or a quantity of the infrared lightchanges if water droplets are attached to the reverse surface of thesubstrate or the reverse surface of the substrate is wet, resulting indifferent measurement results.

Further, in Japanese laid-open patent publication No. 2005-268566, anopen-type air bag in which a substrate holding surface is open tomeasure the temperature of the substrate directly is used. However, inthe open-type air bag, a pressurized fluid leaks during polishing, orwater or a polishing liquid enters an open part of the air bag to hinderaccurate measurement of the temperature. Further, as disclosed inJapanese laid-open patent publication No. 2005-268566, in the case wherethe temperature of the substrate is measured by an infrared radiationthermometer which is widely used, because the infrared light passesthrough a silicon wafer, the infrared radiation thermometer can measureonly a temperature of a wafer having a metal film and is unsuitable formeasuring temperatures of other objects. Further, even if a closed-typeair bag is used and produced from a material for allowingelectromagnetic radiations to pass therethrough, the temperature of thesubstrate cannot be measured with high accuracy because even the air bagcomposed of a thin film inhibits transmission of the electromagneticradiations in some degree.

Further, Japanese laid-open patent publication No. 2006-332520 disclosesa technology for measuring a temperature of a membrane for holding asemiconductor wafer as a means for measuring a temperature near asurface, being polished, of the semiconductor wafer. However, in thetechnology disclosed in Japanese laid-open patent publication No.2006-332520, because the temperature sensor is attached to the membrane,when the membrane as expendables is replaced, it is necessary to replacethe temperature sensor simultaneously. Therefore, this technologynecessitates a very expensive structure, and a work for wiring of thetemperature sensor or the like each time the membrane is replaced, thusdeteriorating productivity.

The inventors of the present invention have intensively studied theconventional technology disclosed in Japanese laid-open patentpublication Nos. 2006-128582, 2002-301660, 2005-268566, 2006-332520 andthe like. As a result, it has been discovered that although it isdesirable to measure a temperature of a substrate such as asemiconductor wafer during polishing, if a membrane for forming apressure chamber cannot be employed, a serious problem that a polishingperformance of the polishing apparatus cannot be maintained arises.Therefore, estimation of the temperature of the substrate duringpolishing by measuring a temperature of a member, for example, amembrane near the substrate based on the premise of employing themembrane for forming the pressure chamber has been discovered to be thebest.

Therefore, the inventors of the present invention have attemptedestimation of a temperature of the substrate during polishing from atemperature of the membrane for forming the pressure chamber bymeasuring the temperature of the membrane with a noncontact-typeinfrared radiation thermometer. Then, several types of membranes aremounted on the substrate holding apparatus (top ring), and experimentsfor measuring temperatures of the membranes by an infrared radiationthermometer and a thermocouple have been conducted repeatedly while thesubstrates held by the membranes are heated and cooled, therebyexamining the relationship of both measurements. As a result, it hasbeen discovered that the measurement value of the temperature of themembrane by the infrared radiation thermometer and the measurement valueof the membrane by the thermocouple coincide generally with each otherin a certain type of membrane, but differ from each other in other typesof membranes (described later).

The inventors of the present invention have analyzed a cause of theabove difference and have found that because the upper surface of themembrane reflects the infrared light, measurement values are affected bytemperatures of parts located around the membrane, and thus thetemperature of the membrane cannot be measured by the infrared radiationthermometer with high accuracy. The membrane is produced by a mold in aforming process. Since the surface of the mold is normally processed bymirror finish, the surface of the membrane also becomes in a mirrorsurface state having small surface roughness. The upper surface of themembrane which is in a mirror surface state has high reflectance of theinfrared light. Thus, in the case where measurement of the infraredradiation temperature is performed from the location above the membrane,measurement value is strongly influenced by the infrared light radiatedfrom the parts located around the membrane, and thus the temperature ofthe membrane cannot be measured with high accuracy.

Further, the inventors of the present invention have discovered that inthe case where the temperature of the membrane is measured by anoncontact-type infrared radiation thermometer, the temperature of themembrane cannot be measured with high accuracy due to dew condensationin the membrane.

The inventors of the present invention have conducted variousexperiments and analyzed the experimental results for finding out acause of the dew condensation in the membrane, and have obtained thefollowing knowledge.

When the substrate is pressed against the polishing pad and is polished,the membrane and a gas in the pressure chamber are heated by processingheat to cause temperature rise. After polishing the substrate, thesubstrate is removed from the substrate holding surface, and then thesubstrate holding surface is cleaned by a cleaning liquid in a cleaningprocess to cool the membrane and the gas in the pressure chamber. Thus,the membrane and the gas in the pressure chamber repeat temperature riseand temperature drop. On the other hand, fluid passages for supplying agas into the pressure chamber are normally connected to a pressurecontroller, a pressure release valve, a vacuum source and the like. As apressurized fluid, an inert gas such as N₂ or dry air from which watercontent is removed is normally used, and hence dew condensation does notoccur. However, when the substrate is held under vacuum by the substrateholding apparatus, the pressure chamber becomes in a vacuum state tohold the substrate under vacuum. Thereafter, when polishing of thesubstrate is started or the substrate is removed from the substrateholding apparatus, the vacuum state is released by exposure to anatmospheric pressure of the pressure chamber. When the fluid passagecommunicating with the pressure chamber is switched from the vacuumstate to the state of the pressure release to an atmospheric pressure,air in the atmosphere in which the polishing apparatus is placed entersthe fluid passage. Thus, air containing water content enters thepressure chamber by this pressure release operation, and the gas in thepressure chamber repeats temperature rise and temperature drop,resulting in dew condensation in the membrane. When water droplets areattached to the upper surface of the membrane due to dew condensation inthe membrane, a quantity of the infrared light radiated from such parthaving water droplets changes compared to the case where there is nowater droplets, and thus the temperature of the membrane cannot bemeasured with high accuracy by the infrared radiation thermometer.Further, as an amount of water droplets caused by dew condensationincreases, water is accumulated in the pressure chamber to change thepressure applied to the substrate, and thus stable polishing cannot becarried out.

The present invention has been made in view of the above circumstances.It is therefore an object of the present invention to provide asubstrate holding apparatus having a membrane for forming a pressurechamber which can control a temperature of a substrate such as asemiconductor wafer by estimating the temperature of the substrateduring polishing.

Further, another aspect of the present invention is to provide apolishing apparatus having such substrate holding apparatus.

In order to achieve the above objects, according to a first aspect ofthe present invention, there is provided a polishing apparatus forpolishing a substrate, comprising: a polishing table having a polishingsurface; a substrate holding apparatus configured to hold the substrateand to press the substrate against the polishing surface; and acontroller; the substrate holding apparatus comprising: an elasticmembrane configured to form a substrate holding surface which is broughtinto contact with the substrate; a carrier provided above the elasticmembrane; at least one pressure chamber formed between the elasticmembrane and the carrier; and an infrared light detector configured tomeasure thermal energy from the elastic membrane; wherein the controllercalculates an estimate value of a temperature of the elastic membraneusing a measured value of the infrared light detector.

According to the present invention, while a substrate such as asemiconductor wafer is held by an elastic membrane and pressed against apolishing surface to polish the substrate, thermal energy radiated fromthe elastic membrane is measured by an infrared light detector, and anestimate value of a temperature of the elastic membrane is calculatedusing a measured value of the infrared light detector by a controller.In this case, a correlation between the measured value of the infraredlight detector and the temperature of the elastic membrane has beenobtained in advance by experiment, and the estimate value of thetemperature of the elastic membrane is calculated using the correlation.Because the elastic membrane constitutes a substrate holding surface forholding the substrate, the elastic membrane is a member which is mostaffected by the temperature of the substrate, and thus the temperatureof the substrate can be estimated indirectly by estimating thetemperature of the elastic membrane.

In a preferred aspect of the present invention, the controllercalculates an estimate value of a temperature of the substrate using theestimate value of the temperature of the elastic membrane.

According to the present invention, an estimate value of a temperatureof the substrate is calculated from the estimate value of thetemperature of the elastic membrane by the controller. In this case, acorrelation between a temperature of the elastic membrane and atemperature of the substrate has been obtained in advance by experiment,and the estimate value of the temperature of the substrate is calculatedusing the correlation.

In a preferred aspect of the present invention, a polishing condition ischanged using the estimate value of the temperature of the elasticmembrane.

According to the present invention, in the case where the estimate valueof the temperature of the elastic membrane or the estimate value of thetemperature of the substrate is high during polishing, a polishingpressure is lowered by lowering a pressure of a pressure chamber tosuppress temperature rise of the substrate or the elastic membrane.Further, the temperature control of the entire surface of the polishingsurface may be performed or the temperature control of a portion of thepolishing surface corresponding to the measured pressure chamber may beperformed using a device for cooling and heating the polishing surfaceprovided outside the substrate holding apparatus. As a device foradjusting a temperature of the polishing surface, there are a device foradjusting the temperature of the polishing surface by bringing a mediuminto contact with the polishing surface, a device for blowing a fluidonto the polishing surface, and the like.

In a preferred aspect of the present invention, the infrared lightdetector comprises an infrared radiation thermometer.

According to the present invention, the temperature of the elasticmembrane can be measured by measuring a quantity of the infrared lightas thermal energy radiated from the elastic membrane as an object to bemeasured.

In order to achieve the above objects, according to a second aspect ofthe present invention, there is provided a substrate holding apparatusfor holding a substrate and pressing the substrate against a polishingsurface, comprising: an elastic membrane configured to form a substrateholding surface which is brought into contact with the substrate; acarrier provided above the elastic membrane; at least one pressurechamber formed between the elastic membrane and the carrier; and aninfrared light detector configured to measure thermal energy from theelastic membrane; wherein surface roughing processing is applied to arear surface side of the substrate holding surface of the elasticmembrane.

According to the present invention, while a substrate such as asemiconductor wafer is held by an elastic membrane and pressed against apolishing surface to polish the substrate, thermal energy radiated fromthe elastic membrane is measured by an infrared light detector. Becausesurface roughing processing is applied to a rear surface side of thesubstrate holding surface of the elastic membrane, the reflectance ofthe infrared light at the rear surface side of the substrate holdingsurface of the elastic membrane is lowered, and thus the infrared lightdetector can measure thermal energy radiated from the elastic membranewith high accuracy. Therefore, the temperature of the elastic membranecan be measured with high accuracy.

In order to achieve the above objects, according to a third aspect ofthe present invention, there is provided a substrate holding apparatusfor holding a substrate and pressing the substrate against a polishingsurface, comprising: an elastic membrane configured to form a substrateholding surface which is brought into contact with the substrate; acarrier provided above the elastic membrane; at least one pressurechamber formed between the elastic membrane and the carrier; an infraredlight detector configured to measure thermal energy from the elasticmembrane; and a measuring instrument disposed at a rear surface side ofthe substrate holding surface of the elastic membrane and configured tomeasure thermal energy of a portion other than the elastic membrane.

According to the present invention, while a substrate such as asemiconductor wafer is held by an elastic membrane and pressed against apolishing surface to polish the substrate, thermal energy radiated fromthe elastic membrane is measured by an infrared light detector, andthermal energy of a portion, other than the elastic membrane, located ata rear surface side of the elastic membrane is measured by a measuringinstrument. Then, the estimate value of the temperature of the elasticmembrane or the estimate value of the temperature of the substrate iscalculated using the measured value of the thermal energy of the elasticmembrane by the infrared light detector and the measured value of thethermal energy of the portion, other than the elastic membrane, by themeasuring instrument. In the case where the infrared light radiated fromthe portion, other than the elastic membrane, located at the rearsurface side of the elastic membrane is reflected from the elasticmembrane to exert a great influence on the infrared light detector, thetemperature of the elastic membrane or the temperature of the substratecannot be estimated by the measured value of the infrared light detectorwith high accuracy. Therefore, the estimate value of the temperature ofthe elastic membrane or the estimate value of the temperature of thesubstrate is calculated using the measured value of the infrared lightdetector and the measured value at the portion, other than the elasticmembrane, by the measuring instrument.

In a preferred aspect of the present invention, the measuring instrumentmeasures the thermal energy of the carrier.

According to the present invention, by measuring the thermal energy ofthe carrier which forms the pressure chamber together with the elasticmembrane, the temperature of the carrier can be measured. In the casewhere the infrared light radiated from the carrier is reflected from theelastic membrane to exert a great influence on the infrared lightdetector, the temperature of the elastic membrane or the temperature ofthe substrate cannot be estimated by the measured value of the infraredlight detector with high accuracy. Therefore, the estimate value of thetemperature of the elastic membrane or the estimate value of thetemperature of the substrate is calculated using the measured value ofthe infrared light detector and the measured value of the temperature ofthe carrier by the measuring instrument.

In a preferred aspect of the present invention, a substrate holdingapparatus further comprises a pressure sensor configured to measure apressure of the pressure chamber.

According to the present invention, the pressure in the pressure chambercan be controlled to a desired value by measuring the pressure of thepressure chamber by a pressure sensor. For example, a first pressurecontroller and a second pressure controller are coupled to one pressurechamber, and the two pressure controllers are set to the same controlpressure at the start of polishing. When the estimate value of thetemperature of the substrate exceeds the predetermined temperatureduring the polishing process, the set pressure of the second pressurecontroller is lowered, while the set pressure of the first pressurecontroller is maintained at the same pressure. Thus, the pressurizedfluid flows from a fluid passage communicating with the first pressurecontroller toward a fluid passage communicating with the second pressurecontroller, and this flow of the pressurized fluid cools the interior ofthe pressure chamber. At this time, the pressure in the pressure chamberis monitored by the pressure sensor, and when the pressure in thepressure chamber drops greatly below the control pressure, the setpressure of the second pressure controller is increased so that adesired pressure is developed in the pressure chamber.

In a preferred aspect of the present invention, a substrate holdingapparatus further comprises a controller configured to calculate anestimate value of a temperature of the elastic membrane using a measuredvalue of the infrared light detector and a measured value of themeasuring instrument.

According to the present invention, the estimate value of thetemperature of the elastic membrane is calculated using the measuredvalue of the thermal energy of the elastic membrane by the infraredlight detector and the measured value of the thermal energy of theportion, other than the elastic membrane, by the measuring instrument.

In a preferred aspect of the present invention, plural sets of ameasured value of a temperature of the elastic membrane, a measuredvalue (T₁) of the infrared light detector, and a measured value (T₂) ofthe measuring instrument are prepared in advance, regressioncoefficients b₀, b₁ and b₂ which minimize (the measured value of thetemperature of the elastic membrane−the estimate value of thetemperature of the elastic membrane)² in a multiple linear regressionequation represented by (the estimate value of the temperature of theelastic membrane)=b₀+b₁×T₁+b₂×T₂ are calculated; and the estimate valueof the temperature of the elastic membrane is calculated by thefollowing equation: (the estimate value of the temperature of theelastic membrane)=b₀+b₁×(the measured value of the temperature of theelastic membrane)+b₂×(the measured value of the measuring instrument).

In a preferred aspect of the present invention, the controllercalculates an estimate value of a temperature of the substrate using theestimate value of the temperature of the elastic membrane and themeasured value of the measuring instrument.

According to the present invention, the estimate value of thetemperature of the substrate is calculated using the measured value ofthe thermal energy of the elastic membrane by the infrared lightdetector and the measured value of the thermal energy of the portion,other than the elastic membrane, by the measuring instrument.

In a preferred aspect of the present invention, plural sets of ameasured value of a temperature of the substrate, the estimate value(T₁) of the temperature of the elastic membrane and the measured value(T₂) of the measuring instrument are prepared in advance, regressioncoefficients b₀, b₁ and b₂ which minimize (the measured value of thetemperature of the substrate−the estimate value of the temperature ofthe substrate)² in a multiple linear regression equation represented by(the estimate value of the temperature of the substrate)=b₀+b₁×T₁+b₂×T₂are calculated, and the estimate value of the temperature of thesubstrate is calculated by the following equation: (the estimate valueof the temperature of the substrate)=b₀+b₁×(the estimate value of thetemperature of the elastic membrane)+b₂×(the measured value of themeasuring instrument).

In a preferred aspect of the present invention, at least two pressurechambers are formed between the elastic membrane and the carrier, andthe infrared light detector is provided in at least one pressure chamberof at least two pressure chambers.

According to the present invention, in the substrate holding apparatushaving a plurality of pressure chambers, an infrared light detector isprovided in one pressure chamber, and from the measurement result ofthis infrared light detector, the pressure of each pressure chamber maybe changed or the polishing conditions such as operation of thetemperature adjusting device of the polishing surface may be changed.Further, two infrared light detectors are provided in two pressurechambers, respectively, and from the measurement results of the twoinfrared light detectors, the temperature of the elastic membrane or thetemperature of the substrate may be estimated by linear interpolation.Further, the infrared light detectors are provided so as to correspondto all of the pressure chambers, and from the measurement results of therespective infrared light detectors, the temperature of the elasticmembrane or the temperature of the substrate at positions correspondingto the respective pressure chambers may be estimated.

In a preferred aspect of the present invention, the substrate holdingsurface of the elastic membrane for forming the pressure chamber inwhich the infrared light detector is provided has no opening.

According to the present invention, because the substrate holdingsurface of the elastic membrane for forming the pressure chamber inwhich the infrared light detector is provided has no opening, when thesubstrate holding surface is cleaned, the cleaning liquid can beprevented from entering the pressure chamber in which the infrared lightdetector is provided. Therefore, water droplets can be prevented fromremaining at the rear surface side of the elastic membrane, and thus theaccuracy of the infrared light detector can be ensured.

In a preferred aspect of the present invention, the infrared lightdetector comprises an infrared radiation thermometer.

According to the present invention, the temperature of the elasticmembrane can be measured by measuring a quantity of the infrared lightas thermal energy radiated from the elastic membrane as an object to bemeasured.

In order to achieve the above objects, according to a fourth aspect ofthe present invention, there is provided a polishing apparatuscomprising: a polishing table having a polishing surface; and asubstrate holding apparatus according to any one of claims 5 to 15.

In order to achieve the above objects, according to a fifth aspect ofthe present invention, there is provided a polishing apparatus forpolishing a substrate, comprising: a polishing table having a polishingsurface; a substrate holding apparatus configured to hold the substrateand to press the substrate against the polishing surface; the substrateholding apparatus comprising: an elastic membrane configured to form asubstrate holding surface which is brought into contact with thesubstrate; a carrier provided above the elastic membrane; at least onepressure chamber formed between the elastic membrane and the carrier;and a first passage communicating with the pressure chamber; wherein thefirst passage is connected only to a gas source isolated from anatmosphere in which the polishing apparatus is placed.

According to the present invention, when the pressure of the pressurechamber increases from the vacuum state to an atmospheric pressure, agas can be supplied to the pressure chamber from a gas source isolatedfrom the atmosphere in which the polishing apparatus is placed.Therefore, air containing water content can be prevented from enteringthe pressure chamber, and thus dew condensation on the elastic membranein the pressure chamber does not occur.

In order to achieve the above objects, according to a sixth aspect ofthe present invention, there is provided a polishing apparatus forpolishing a substrate, comprising: a polishing table having a polishingsurface; a substrate holding apparatus configured to hold the substrateand to press the substrate against the polishing surface; the substrateholding apparatus comprising: an elastic membrane configured to form asubstrate holding surface which is brought into contact with thesubstrate; a carrier provided above the elastic membrane; at least onepressure chamber formed between the elastic membrane and the carrier;and a first passage communicating with the pressure chamber; whereinonly a gas whose dew-point temperature is not more than 20° C. under anatmospheric pressure is supplied to the pressure chamber.

According to the present invention, even if the elastic membrane iscooled by deionized water (pure water) used for cleaning the top ring orthe like, when the pressure of the pressure chamber increases from thevacuum state to an atmospheric pressure, only a gas whose dew-pointtemperature under atmospheric pressure is not more than 20° C. issupplied to the pressure chamber. Therefore, dew condensation on theelastic membrane in the pressure chamber does not occur.

According to the present invention, the temperature of a substrate suchas a semiconductor wafer can be controlled by estimating the temperatureof the substrate. More specifically, the present invention has thefollowing effects:

(1) When the temperature of the substrate increases during polishing,the rigidity of the polishing pad is lowered to deteriorateplanarization characteristics of polishing. This is because concaveportions of unevenness of the pattern surface on the substrate are alsopolished due to a lowering of the rigidity of the polishing pad, andthus removal of the step height finally cannot be sufficientlyperformed. According to the present invention, the temperature of thesubstrate can be estimated with high accuracy, and if the substratetemperature becomes a predetermined value or higher, the polishingconditions or the like are changed, thereby suppressing temperature riseof the substrate.

(2) Because the polishing slurry causes chemical change on the surfaceof the substrate, reaction temperature is very important parameter.According to the present invention, because the temperature of thesubstrate can be estimated with high accuracy, the substrate can bepolished at a temperature range which fits characteristics of thepolishing slurry in various processes. For example, in the process inwhich the polishing rate is lowered at a polishing temperature of apredetermined value or higher, the substrate temperature is estimatedwith high accuracy, and the polishing conditions are changed so as notto increase the substrate temperature to the predetermined value orhigher. In contrast, in the case where the polishing rate is lowered ata polishing temperature of a predetermined value or lower, the polishingconditions are changed so as not to decrease the substrate temperatureto the predetermined value or lower. Further, in the process in whichdefects on the substrate (such as foreign matter on the substrate orscratches on the substrate), step height removal performance, polishingstability, and the like have dependency on the polishing temperatureother than the polishing rate, the polishing temperature can becontrolled in consideration of the effect on the defects on thesubstrate, the step height removal performance, the polishing stability,and the like.

(3) According to the present invention, because the temperature of thesubstrate can be estimated with high accuracy, the distribution of thetemperature within the surface of the substrate can be grasped with highaccuracy. Then, by controlling the distribution of the temperaturewithin the surface of the substrate so as to be uniformized, thepolishing characteristics within the surface of the substrate can becontrolled uniformly, or the temperature of the surface of the substratecan be controlled so as to have any distribution of the temperature. Forexample, in the case where the distribution of the film thickness on thesubstrate is not uniform before polishing, in order to uniformize thedistribution of the film thickness on the substrate after polishing,controlling the temperature of the substrate so as to have distributionof the temperature within the surface of the substrate can be utilizedfor intentionally creating the distribution of the temperature withinthe surface of the substrate during polishing.

Further, according to the present invention, because estimate of thetemperature of the membrane (elastic membrane) as well as estimate ofthe temperature of the substrate can be made, the following effects canbe obtained.

(1) By estimating the temperature of the membrane, the above effect ofestimate of the temperature of the substrate can be obtained indirectly.

(2) The membrane is thermally expanded by its temperature. Because theretainer ring is located at the outer circumferential side of themembrane, if the thermal expansion of the membrane becomes large, theexpanded outer circumferential side of the membrane is brought intocontact with the inner circumferential side of the retainer ring, andthus the outer circumferential side of the membrane is restrained. Then,wrinkles are formed in the membrane or the membrane is deformed, thushindering pressurization to the substrate by the membrane. According tothe present invention, because the temperature of the membrane can begrasped, an amount of thermal expansion of the membrane can be grasped,and the temperature of the membrane can be controlled so as not to bringthe membrane into contact with the retainer ring.

(3) When the temperature of the membrane increases, the hardness of themembrane is lowered (the membrane becomes soft), and thus especially thepressure applied to the substrate at an outer circumferential portion ofthe substrate is changed. Normally, the substrate is pressed byinflating the outer circumferential portion of the membrane. When thehardness of the membrane is lowered, the tension of rubber required forinflating the membrane is lowered to reduce the loss of the pressure ofthe air bag (pressure applied to the membrane) due to the tension of therubber. As a result, higher pressure than expected is applied to thesubstrate. According to the present invention, because the temperatureof the membrane can be grasped and controlled, the hardness of themembrane can be maintained within a certain range, and thus the pressingforce applied to the substrate can be maintained at a desired constantvalue. Further, the pressure of the air bag can be controlled to makethe pressing force applied to the substrate constant based on thetemperature of the membrane. Specifically, when the temperature of themembrane increases, the membrane becomes soft to reduce the pressure ofthe air bag.

Further, according to the present invention, when the pressure of thepressure chamber increases from the vacuum state to an atmosphericpressure, the gas can be supplied to the pressure chamber from the gassource isolated from the atmosphere in which the polishing apparatus isplaced. Therefore, air containing water content can be prevented fromentering the pressure chamber. Thus, dew condensation on the elasticmembrane in the pressure chamber does not occur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an entire structure of a polishingapparatus according to an embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view showing a top ringconstituting a substrate holding apparatus for holding a semiconductorwafer as an object to be polished and pressing the semiconductor waferagainst a polishing surface on a polishing table;

FIG. 3 is a schematic cross-sectional view showing main structuralelements of the top ring;

FIG. 4 is a schematic cross-sectional view showing an experimentalapparatus for measuring temperature of a wafer, temperature of amembrane, temperature of a carrier, and the like when a semiconductorwafer (substrate) is heated and cooled;

FIG. 5 is a graph in which time variations of the temperatures areplotted when the lower surface of the semiconductor wafer (substrate) isheated by forced heating, and then cooled by forced cooling using theexperimental apparatus shown in FIG. 4;

FIGS. 6A and 6B are graphs in which the measured values of the infraredradiation thermometer are plotted on the horizontal axis and themeasured values of the temperature of the membrane upper surface by thethermocouple at the same time are plotted on the vertical axis using alltime-series data shown in FIG. 5;

FIGS. 7A and 7B are graphs in which the correction values of theinfrared radiation temperature measurement are plotted on the horizontalaxis and the measured values of the temperature of the membrane uppersurface at the same time by the thermocouple are plotted on the verticalaxis;

FIGS. 8A and 8B are graphs in which the estimate values of the membranetemperature calculated by a membrane temperature estimate equation areplotted on the horizontal axis and the measured values of thetemperature of the membrane upper surface by the thermocouple at thesame time are plotted on the vertical axis;

FIG. 9 is a graph showing the results in which the membrane temperaturesare estimated from the measured values of the infrared radiationthermometer and the measured values of the carrier temperature in FIG. 5by using the multiple linear regression equation;

FIG. 10 is a graph in which the estimate values of the membranetemperature calculated by the membrane temperature estimate equation areplotted on the horizontal axis and the measured values of thetemperature of the wafer lower surface by the thermocouple at the sametime are plotted on the vertical axis using all time-series data shownin FIG. 5;

FIG. 11 is a graph in which the estimate values of the wafer temperatureare plotted on the horizontal axis and the measured values of thetemperature of the wafer lower surface by the thermocouple at the sametime are plotted on the vertical axis;

FIG. 12 is a graph showing the results in which the wafer temperaturesare estimated using the multiple linear regression equation from themeasured values of the infrared radiation thermometer and the measuredvalues of the carrier temperature in the case of FIG. 5;

FIG. 13 is a flow chart showing one aspect of a process for determiningpolishing conditions and the like by estimating the wafer temperaturefrom the measured value of the infrared radiation thermometer and themeasured value of the carrier temperature performed in the polishingapparatus according to the present invention;

FIG. 14A is an enlarged view of XIV part of FIG. 2 and FIG. 14B is aview showing a piping system for supplying N₂ having an atmosphericpressure into the pressure chamber;

FIG. 15 is a schematic cross-sectional view of the top ring havingstructure for performing the temperature control of the pressurechamber;

FIG. 16 is a schematic plan view showing an arrangement of the polishingliquid supply nozzle for supplying the polishing slurry (polishingliquid), the polishing pad, and the top ring;

FIG. 17 is a schematic plan view showing an example of the temperaturecontrolling device for the polishing pad;

FIG. 18 is a schematic plan view showing another example of thetemperature controlling device for the polishing pad;

FIG. 19 is a schematic plan view showing an example in which thedressing load (dress load) and/or the scanning speed is changed;

FIG. 20 is a schematic plan view showing an example of changing thedropping position of the polishing slurry in accordance with thetemperature of the wafer;

FIG. 21 is a schematic plan view showing an example in which thetemperature (distribution) of the polishing pad surface is measuredsimultaneously with the wafer temperature measurement and thetemperature control is performed based on the measurement results; and

FIG. 22 is a cross-sectional view showing more detailed structures ofthe top ring having the infrared radiation thermometer and thethermocouple for measuring the carrier temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A polishing apparatus according to embodiments of the present inventionwill be described below with reference to FIGS. 1 through 22. Like orcorresponding parts are denoted by like or corresponding referencenumerals throughout drawings and will not be described belowrepetitively.

FIG. 1 is a schematic view showing an entire structure of a polishingapparatus according to an embodiment of the present invention. As shownin FIG. 1, the polishing apparatus comprises a polishing table 100, anda top ring 1 for holding a substrate such as a semiconductor wafer as anobject to be polished and pressing the substrate against a polishingsurface on the polishing table 100.

The polishing table 100 is coupled via a table shaft 100 a to a motor(not shown) disposed below the polishing table 100. Thus, the polishingtable 100 is rotatable about the table shaft 100 a. A polishing pad 101is attached to an upper surface of the polishing table 100. An uppersurface 101 a of the polishing pad 101 constitutes a polishing surfaceto polish a semiconductor wafer W. A polishing liquid supply nozzle 102is provided above the polishing table 100 to supply a polishing liquid(polishing slurry) Q onto the polishing pad 101 on the polishing table100.

Various kinds of polishing pads are available on the market. Forexample, some of these are SUBA800, IC-1000, and IC-1000/SUBA400(two-layer cloth) manufactured by Nitta-Haas Inc., and Surfin xxx-5 andSurfin 000 manufactured by Fujimi Inc. SUBA800, Surfin xxx-5, and Surfin000 are non-woven fabrics bonded by urethane resin, and IC-1000 is madeof rigid foamed polyurethane (single layer). Foamed polyurethane isporous and has a large number of fine recesses or holes formed in itssurface.

The top ring 1 basically comprises a top ring body 2 for pressing asemiconductor wafer W against the polishing surface 101 a, and aretainer ring 3 for holding an outer peripheral edge of thesemiconductor wafer W to prevent the semiconductor wafer W from beingslipped out of the top ring.

The top ring 1 is connected to a top ring shaft 111, and the top ringshaft 111 is vertically movable with respect to a top ring head 110 by avertically movable mechanism 124. When the top ring shaft 111 movesvertically, the top ring 1 is lifted and lowered as a whole forpositioning with respect to the top ring head 110. A rotary joint 25 ismounted on the upper end of the top ring shaft 111. The verticalmovement mechanism 124, which vertically moves the top ring shaft 111and the top ring 1, has a bridge 128 supporting the top ring shaft 111in a manner such that the top ring shaft 111 is rotatable via a bearing126, a ball screw 132 mounted on the bridge 128, a support stage 129which is supported by poles 130, and an AC servomotor 138 provided onthe support stage 129. The support stage 129, which supports theservomotor 138, is fixed to the top ring head 110 via the poles 130.

The ball screw 132 has a screw shaft 132 a which is coupled to theservomotor 138, and a nut 132 b into which the screw shaft 132 a isthreaded. The top ring shaft 111 is configured to be vertically movabletogether with the bridge 128. Accordingly, when the servomotor 138 isdriven, the bridge 128 is vertically moved through the ball screw 132.As a result, the top ring shaft 111 and the top ring 1 are verticallymoved.

Further, the top ring shift 111 is connected to a rotary sleeve 112 by akey (not shown). The rotary sleeve 112 has a timing pulley 113 fixedlydisposed therearound. A top ring motor 114 is fixed to the top ring head110. The timing pulley 113 is operatively coupled to a timing pulley 116provided on the top ring motor 114 by a timing belt 115. Therefore, whenthe top ring motor 114 is driven, the timing pulley 116, the timing belt115 and the timing pulley 113 are rotated to rotate the rotary sleeve112 and the top ring shaft 111 in unison with each other, thus rotatingthe top ring 1. The top ring head 110 is supported on a top ring headshaft 117 which is rotatably supported by a flame (not shown). Thepolishing apparatus has a controller 50 for controlling respectiveapparatuses including the top ring motor 114, the servomotor 138, thepolishing table motor and the like.

In the polishing apparatus constructed as shown in FIG. 1, the top ring1 is configured to hold a substrate such as a semiconductor wafer W onits lower surface. The top ring head 110 is pivotable about the top ringshaft 117. Thus, the top ring 1, which holds the semiconductor wafer Won its lower surface, is moved from a position at which the top ring 1receives the semiconductor wafer W to a position above the polishingtable 100 by pivitable movement of the top ring head 110. Then, the topring 1 is lowered to press the semiconductor wafer W against the surface(polishing surface) 101 a of the polishing pad 101. At this time, whilethe top ring 1 and the polishing table 100 are respectively rotated, apolishing liquid is supplied onto the polishing pad 101 from thepolishing liquid supply nozzle 102 provided above the polishing table100. In this manner, the semiconductor wafer W is brought into slidingcontact with the polishing surface 101 a of the polishing pad 101 a.Thus, a surface of the semiconductor wafer W is polished.

Next, the top ring (polishing head) of the polishing apparatus accordingto the present invention will be described below with reference to FIG.2. FIG. 2 is a schematic cross-sectional view showing the top ring 1constituting a substrate holding apparatus for holding a semiconductorwafer W as an object to be polished and pressing the semiconductor waferW against a polishing surface on a polishing table. FIG. 2 shows onlymain structural elements constituting the top ring 1.

As shown in FIG. 2, the top ring 1 basically comprises a top ring body(described also as carrier) 2 for pressing a semiconductor wafer Wagainst the polishing surface 101 a, and a retainer ring 3 for directlypressing the polishing surface 101 a. The top ring body (carrier) 2 isin the form of a circular plate, and the retainer ring 3 is attached toa peripheral portion of the top ring body 2. The top ring body 2 is madeof resin such as engineering plastics (e.g., PEEK). As shown in FIG. 2,the top ring 1 has an elastic membrane 4 attached to a lower surface ofthe top ring body 2. The elastic membrane 4 is brought into contact witha rear face of a semiconductor wafer held by the top ring 1. The elasticmembrane 4 is made of a highly strong and durable rubber material suchas ethylene propylene rubber (EPDM), polyurethane rubber, siliconerubber, or the like. The elastic membrane 4 constitutes a substrateholding surface for holding the substrate such as a semiconductor wafer.

The elastic membrane 4 has a plurality of concentric partition walls 4a, and a circular central chamber 5, an annular ripple chamber 6, anannular outer chamber 7 and an annular edge chamber 8 are defined by thepartition walls 4 a between the upper surface of the elastic membrane 4and the lower surface of the top ring body 2. Specifically, the centralchamber 5 is defined at the central portion of the top ring body 2, andthe ripple chamber 6, the outer chamber 7 and the edge chamber 8 areconcentrically defined in the order from the central portion to theperipheral portion of the top ring body 2. A passage 11 communicatingwith the central chamber 5, a passage 12 communicating with the ripplechamber 6, a passage 13 communicating with the outer chamber 7 and apassage 14 communicating with the edge chamber 8 are formed in the topring body 2. The passage 11 communicating with the central chamber 5,the passage 13 communicating with the outer chamber 7, and the passage14 communicating with the edge chamber 8 are connected to a passage 21,a passage 23 and a passage 24, respectively via a rotary joint 25. Thepassage 21, the passage 23 and the passage 24 are connected to apressure regulating unit 30 through respective valves V1-1, V3-1 andV4-1 and pressure regulators R1, R3 and R4. Further, the passage 21, thepassage 23 and the passage 24 are connected to a vacuum source 31through respective valves V1-2, V3-2 and V4-2 and are capable ofcommunicating with the atmosphere through the respective valves V1-3,V3-3 and V4-3.

On the other hand, the passage 12 communicating with the ripple chamber6 is connected to a passage 22 through the rotary joint 25. Then, thepassage 22 is connected to the pressure regulating unit 30 through agas-liquid separator 35, a valve V2-1 and a pressure regulator R2.Further, the passage 22 is connected to a vacuum source 131 through thegas-liquid separator 35 and a valve V2-2 and is capable of communicatingwith the atmosphere through the valve V2-3.

Further, a retainer ring pressure chamber 9 composed of an elasticmembrane is formed immediately above the retainer ring 3, and theretainer ring pressure chamber 9 is connected via a passage 15 formed inthe top ring body (carrier) 2 and the rotary joint 25 to the passage 26.Then, the passage 26 is connected to the pressure regulating unit 30through a valve V5-1 and a pressure regulator R5. Further, the passage26 is connected to the vacuum source 31 through a valve V5-2 and iscapable of communicating with the atmosphere through a valve V5-3. Thepressure regulators R1, R2, R3, R4 and R5 have pressure regulatingfunction for regulating pressures of a pressurized fluid supplied fromthe pressure regulating unit 30 to the central chamber 5, the ripplechamber 6, the outer chamber 7, the edge chamber 8 and the retainer ringpressure chamber 9, respectively. The pressure regulators R1, R2, R3, R4and R5 and the valves V1-1-V1-3, V2-1-V2-3, V3-1-V3-3, V4-1-V4-3 andV5-1-V5-3 are connected to the controller 50 (see FIG. 1), andoperations of these pressure regulators and valves are controlled by thecontroller 50. Further, pressure sensors P1, P2, P3, P4 and P5 and flowrate sensors F1, F2, F3, F4 and F5 are provided in the passages 21, 22,23, 24 and 26, respectively.

In the top ring 1 as shown in FIG. 2, the central chamber 5 is definedat the central portion of the top ring body 2, and the ripple chamber 6,the outer chamber 7 and the edge chamber 8 are concentrically defined inthe order from the central portion to the peripheral portion of the topring body 2. Pressures of the fluid supplied to the central chamber 5,the ripple chamber 6, the outer chamber 7, the edge chamber 8, and theretainer ring pressure chamber 9 are independently controlled by thepressure regulating unit 30 and the pressure regulators R1, R2, R3, R4and R5. With this structure, the pressing forces for pressing thesemiconductor wafer W against the polishing pad 101 can be adjusted atrespective areas of the semiconductor wafer and the pressing force forpressing the polishing pad 101 by the retainer ring 3 can be adjusted.

Next, sequential polishing operations of the polishing apparatus shownin FIGS. 1 and 2 will be described below.

The top ring 1 receives and holds under vacuum a semiconductor wafer Wfrom a substrate transfer device (pusher). Thereafter, the top ring 1holding the semiconductor wafer W under vacuum is lowered to a presetpolishing position of the top ring which has been set in advance. Theretainer ring 3 is brought into contact with the surface (polishingsurface) 101 a of the polishing pad 101 at the preset polishingposition. Before the semiconductor wafer W is polished, since thesemiconductor wafer W is attracted to and held by the top ring 1, thereis a small gap of about 1 mm, for example, between the lower surface(the surface to be polished) of the semiconductor wafer W and thepolishing surface 101 a of the polishing pad 101. At this time, thepolishing table 100 and the top ring 1 are being rotated about their ownaxes. In this state, the elastic membrane 4 located at the upper surface(the reverse surface) of the semiconductor wafer W is inflated under thepressure of a fluid supplied thereto to press the lower surface (thesurface to be polished) of the semiconductor wafer W against thepolishing surface of the polishing pad 101. As the polishing table 100and the top ring 1 are being moved relatively to each other, the lowersurface (the surface to be polished) of the semiconductor wafer W ispolished to a predetermined state, e.g., a predetermined film thickness.After polishing of the semiconductor wafer W is finished on thepolishing pad 101, the top ring 1 holds the semiconductor wafer W undervacuum, and the top ring 1 is lifted and moved to the substrate transferdevice (pusher), and then the polished semiconductor wafer W is removed(released) from the top ring 1.

FIG. 3 is a schematic cross-sectional view showing main structuralelements of the top ring 1. As shown in FIG. 3, the top ring 1 basicallycomprises a top ring body 2 for pressing a semiconductor wafer(substrate) W against the polishing pad 101, and a retainer ring 3 fordirectly pressing the polishing surface 101 a. The top ring body 2comprises a top ring flange 41 located at an upper part, a top ringspacer 42 located at an intermediate part, and a carrier 43 located at alower part.

The elastic membrane 4 has a plurality of concentric partition walls 4a, and a circular central chamber 5, an annular ripple chamber 6, anannular outer chamber 7 and an annular edge chamber 8 are defined by thepartition walls 4 a between the upper surface of the elastic membrane 4and the lower surface of the top ring body 2. Specifically, the centralchamber 5 is defined at the central portion of the top ring body 2, andthe ripple chamber 6, the outer chamber 7 and the edge chamber 8 areconcentrically defined in the order from the central portion to theperipheral portion of the top ring body 2. A passage 11 communicatingwith the central chamber 5, a passage 12 communicating with the ripplechamber 6, a passage 13 communicating with the outer chamber 7 and apassage 14 communicating with the edge chamber 8 are formed in the topring body 2. Then, the passage 11 communicating with the central chamber5, the passage 12 communicating with the ripple chamber 6, the passage13 communicating with the outer chamber 7 and the passage 14communicating with the edge chamber 8 are connected via the rotary joint25 (see FIG. 1) to respective pressure chamber pressurizing lines (notshown). The respective pressure chamber pressurizing lines are connectedto the pressure regulating unit 30 (see FIG. 2) through the pressureregulators R1, R2, R3 and R4 (see FIG. 2).

Further, a retainer ring pressure chamber 9 is formed by an elasticmembrane 32 immediately above the retainer ring 3. The elastic membrane32 is housed in a cylinder 33 fixed to the top ring flange 41. Theretainer ring pressure chamber 9 is connected via a passage 15 formed inthe top ring body 2 and the rotary joint 25 (see FIG. 1) to the pressurechamber pressurizing line (not shown). Then, the pressure chamberpressurizing line for the retainer ring pressure chamber 9 is connectedvia the pressure regulator R5 (see FIG. 2) to the pressure regulatingunit 30 (see FIG. 2).

As shown in FIG. 3, four infrared radiation thermometers 45 are providedin the carrier 43 of the top ring 1. Specifically, the four infraredradiation thermometers 45 face the central chamber 5, the ripple chamber6, the outer chamber 7 and the edge chamber 8, respectively so that theinfrared radiation thermometers 45 can measure temperatures at therespective portions of the membrane 4 corresponding to the respectivepressure chambers 5, 6, 7 and 8. Further, a thermocouple 48 is attachedto the upper surface of the carrier 43 of the top ring 1 so that thethermocouple 48 can measure a temperature of the carrier 43. Therespective infrared radiation thermometers 45 and the thermocouple 48are connected to a cold junction temperature sensor unit 46 throughwiring.

According to the present invention, the temperatures of the membrane 4are measured by the infrared radiation thermometers 45, and thetemperature of the substrate is estimated using the measuredtemperatures of the membrane. A thermopile element is installed in theinfrared radiation thermometer 45. An infrared light radiated from themembrane 4 as an object to be measured is incident on the thermopileelement, and a thermal electromotive force corresponding to a quantityof the infrared light incident on the thermopile element is outputted.In the present embodiment, the thermal electromotive force correspondingto K thermocouple output is outputted. This thermal electromotive forceis applied to the cold junction temperature sensor unit 46 through awiring from the infrared radiation thermometer 45. The cold junctiontemperature sensor unit 46 has a sensor for measuring a temperature ofthe atmosphere. The thermal electromotive force is converted into atemperature corresponding to the K thermocouple in the cold junctiontemperature sensor unit 46, and a temperature obtained by adding themeasured cold junction temperature to the converted temperature becomesmeasurement temperature. The cold junction temperature sensor unit 46has an analog-to-digital converter, and the measurement temperature isconverted into a digital signal by the analog-to-digital converter, andthen the digital signal is transmitted to a data receiving unit 47.

Since the thermal electromotive force from the infrared radiationthermometer 45 is very small, measures against noise such as winding ashielded wire around the wiring are taken. Further, in the case wherethe thermocouple output is connected by a connector, it is necessary toproduce the connector from a metal which is the same kind as the Kthermocouple. In this manner, a quantity of the infrared light radiatedfrom the membrane 4 is measured, but a difference occurs between themeasured value and an actual membrane temperature. Because the uppersurface of the membrane 4 has a certain level of reflectance of theinfrared light in many cases, the infrared light radiated from thecarrier 43 of the top ring 1 is reflected from the membrane 4, and thereflected light is measured by the infrared radiation thermometer 45.Therefore, the infrared radiation thermometer 45 is influenced by bothof the infrared light from the membrane 4 and the infrared light fromthe carrier 43. In order to minimize this influence, surface texturingis applied to the upper surface of the membrane to lower the reflectanceof the infrared light, thereby improving measurement accuracy. Thesurface texturing is a processing for forming minute unevenness on thesurface of the membrane. By forming minute unevenness on the uppersurface of the membrane to make surface roughness of the upper surfaceof the membrane rough, the reflectance of the infrared light can belowered. Therefore, the infrared light radiated from the carrier 43 tothe membrane 4 can be prevented from being reflected from the membrane4. Thus, the infrared radiation thermometer 45 can measure a quantity ofthe infrared light radiated from the membrane 4 as an object to bemeasured with high accuracy. In this manner, the reflectance of themembrane 4 can be lowered to diminish the effect of the infrared lightfrom the carrier 43, and the temperature of the membrane 4 is measuredby the infrared radiation thermometer 45, and then the temperature ofthe substrate can be estimated using the measured temperature of themembrane.

Further, in the case where surface texturing is not applied to the uppersurface of the membrane, the infrared radiation thermometer 45 isinfluenced by both of the infrared light from the membrane 4 and theinfrared light from the carrier 43. Therefore, by measuring thetemperature of the carrier 43 with the thermocouple 48 and using themeasured value of the infrared radiation thermometer 45 and the measuredvalue of the thermocouple 48, the temperature of the wafer can beestimated with high accuracy. The temperature measurement of the carriermay be carried out by a noncontact-type thermometer in the same manneras that of the membrane or by a contact-type thermocouple. In the caseof using the contact-type thermocouple, the thermocouple is connected tothe cold junction temperature sensor unit 46 as in the case of theinfrared radiation thermometer 45 for measuring the temperature of themembrane, and the measured temperature is transmitted to the datareceiving unit.

Next, a method for calculating an estimate value of wafer temperatureusing the measured value of the infrared radiation thermometer and themeasured value of the carrier temperature will be describe below. FIG. 4is a schematic cross-sectional view showing an experimental apparatusfor measuring temperature of the wafer, temperature of the membrane,temperature of the carrier, and the like when a semiconductor wafer(substrate) W is heated and cooled. As shown in FIG. 4, an infraredradiation thermometer 45 is installed in the carrier 43 of the top ring1. A thermocouple 48 is attached to the upper surface of the carrier 43.A thermocouple 49 is attached to the upper surface of the membrane 4. Athermocouple 51 is attached to a lower surface of the semiconductorwafer W. Further, a wafer heating and cooling device 52 for heating andcooling the semiconductor wafer W is provided.

The lower surface of the semiconductor wafer W is heated by forcedheating, and then cooled by forced cooling by using the experimentalapparatus shown in FIG. 4, and the measured value of the temperature ofthe wafer lower surface by the thermocouple, the measured value of thetemperature of the membrane upper surface by the thermocouple, themeasured value of the infrared radiation thermometer, and the measuredvalue of the temperature of the carrier are obtained. Specifically, thetemperature of the wafer lower surface is measured by the thermocouple51, the temperature of the membrane upper surface is measured by thethermocouple 49, the infrared radiation temperature is measured by theinfrared radiation thermometer 45, and the temperature of the carrier ismeasured by the thermocouple 48. In this case, it is considered that themeasured value obtained by the contact-type thermocouple has thesmallest error. In FIG. 4, although the thermometer is provided only inthe central chamber 5 for simplifying explanation, respectivetemperatures in other pressure chambers such as the ripple chamber 6,the outer chamber 7, and the like may be measured simultaneously.

FIG. 5 is a graph in which time variations of the temperatures areplotted when the lower surface of the semiconductor wafer (substrate) Wis heated by forced heating, and then cooled by forced cooling using theexperimental apparatus shown in FIG. 4. As shown in FIG. 5, because thesemiconductor wafer is heated by forced heating from the lower surfaceside of the semiconductor wafer, temperature rise of the semiconductorwafer is the fastest, and then temperature rise of the upper surface ofthe membrane occurs, and temperature rise of the carrier is the slowest.Thereafter, in the case where the lower surface side of thesemiconductor wafer is shifted to the forced cooling, temperature dropof the semiconductor wafer is the fastest, and then temperature drop ofthe upper surface of the membrane occurs, and temperature drop of thecarrier is the slowest. The measured values of the infrared radiationthermometer and the measured values of the upper surface of the membraneshow approximately the same tendency at the time of heating and at thetime of cooling.

FIGS. 6A and 6B are graphs in which the measured values of the infraredradiation thermometer are plotted on the horizontal axis and themeasured values of the temperature of the membrane upper surface by thethermocouple at the same time are plotted on the vertical axis using alltime-series data shown in FIG. 5. FIG. 6A shows the measured results inthe pressure chamber having no surface texturing on the upper surface ofthe membrane, and FIG. 6B shows the measured results in the pressurechamber having surface texturing (surface roughing processing isapplied) on the upper surface of the membrane. As shown in FIG. 6A, inthe case of the membrane upper surface having no surface texturing,there is some deviation between the measured values of the infraredradiation thermometer and the measured values of the temperature of themembrane upper surface by the thermocouple at the time of heating and atthe time of cooling, and thus the plotted results become gentle curves.As shown in FIG. 6B, in the case of the membrane upper surface havingsurface texturing, there is some deviation between the measured valuesof the infrared radiation thermometer and the measured values of thetemperature of the membrane upper surface by the thermocouple at thetime of heating and at the time of cooling, and thus the plotted resultsbecome gentle curves. However, in FIG. 6B, because the degree of thedeviation is small, the plotted results become curves close to astraight line. In this manner, in both of the pressure chamber having nosurface texturing and the pressure chamber having surface texturing,there is some deviation between the measured values of the temperatureof the membrane by the infrared radiation thermometer and the measuredvalues of the temperature of the membrane by the thermocouple, andtherefore the effect of the deviation is removed by linearapproximation. Specifically,An output value of thermocouple (estimate value of membranetemperature)=coefficient a×the measured value of the infrared radiationthermometer+coefficient b  equation (1)

By obtaining the coefficient a and the coefficient b which satisfy therelationship of the equation (1), the temperature of the membrane can beestimated by simple linear regression analysis. Hereinafter, theestimate value of the temperature of the membrane by the simple linearregression equation is referred to as correction value of the infraredradiation thermometer measurement.

FIGS. 7A and 7B are graphs in which the correction values of theinfrared radiation temperature measurement are plotted on the horizontalaxis and the measured values of the temperature of the membrane uppersurface at the same time by the thermocouple are plotted on the verticalaxis. Specifically, FIGS. 7A and 7B are graphs showing the relationshipbetween the correction values of the infrared radiation thermometermeasurement and the measured values of the thermocouple after linearapproximation. FIG. 7A shows the results at the area having no surfacetexturing on the upper surface of the membrane, and FIG. 7B shows theresults at the area having surface texturing on the upper surface of themembrane.

FIG. 7A shows that the correction values of the membrane temperaturemeasurement by the infrared radiation thermometer are lower than theactual membrane temperatures measured by the thermocouple at the time offorced heating. Specifically, because temperature rise of the carrier isdelayed at the time of forced heating, the infrared light radiated fromthe low-temperature carrier is reflected from the membrane, and thereflected infrared light is incident on the infrared radiationthermometer. Therefore, the correction values of the measurement arelower than the actual membrane temperatures. In contrast, the correctionvalues of the membrane temperature measurement by the infrared radiationthermometer are higher than the actual membrane temperatures measured bythe thermocouple at the time of forced cooling. Specifically, becausetemperature drop of the carrier is delayed at the time of forcedcooling, the infrared light radiated from the high-temperature carrieris reflected from the membrane, and the reflected infrared light isincident on the infrared radiation thermometer. Therefore, thecorrection values of the measurement are higher than the actual membranetemperatures.

In FIG. 7B, because surface texturing is applied to the upper surface ofthe membrane, the infrared light radiated from the carrier is diffuselyreflected from the upper surface of the membrane, and thus the effect ofthe reflected infrared light on the measured values of the infraredradiation thermometer becomes small. Therefore, the actual membranetemperatures measured by the thermocouple and the correction values ofthe membrane temperature measurement by the infrared radiationthermometer coincide generally with each other at the time of forcedheating and at time of forced cooling. Thus, it can be confirmed that inthe membrane having the upper surface to which surface texturing isapplied, the membrane temperature can be estimated with relatively highaccuracy by the infrared radiation thermometer.

As described above, FIGS. 7A and 7B show that especially in the casewhere surface texturing is not applied to the upper surface of themembrane, when the infrared light radiated from the carrier is reflectedfrom the upper surface of the membrane to exert a large influence on themeasured values of the infrared radiation thermometer, the membranetemperature cannot be estimated with high accuracy from the correctionvalue of the measurement by the infrared radiation thermometer. In thismanner, because the measured values of the infrared radiationthermometer are affected by the temperature of the carrier, the estimatevalue of the membrane temperature is calculated by multiple linearregression analysis which uses the correction values of the infraredradiation thermometer measurement and the measured values of the carriertemperature. In this multiple linear regression analysis, regressioncoefficients b₀, b₁ and b₂ which minimize (the measured value of themembrane temperature by the thermocouple−the estimate value of themembrane temperature)² are calculated. Specifically, the multiple linearregression analysis which uses a method of least squares is employed.(The estimate value of the membrane temperature)=b ₀ +b ₁×(thecorrection value of the infrared radiation thermometer measurement)+b₂×(the measured value of the carrier temperature)  equation (2)

FIGS. 8A and 8B are graphs in which the estimate values of the membranetemperature are plotted on the horizontal axis and the measured valuesof the temperature of the membrane upper surface by the thermocouple atthe same time are plotted on the vertical axis in the case whereregression coefficients b₀, b₁ and b₂ which minimize (the measured valueof the membrane temperature by the thermocouple−the estimate value ofthe membrane temperature)² by multiple linear regression analysisrepresented by the equation (2) are calculated by application of theactual measured values. FIG. 8A shows the case in which the membraneupper surface does not have surface texturing, and FIG. 8B shows thecase in which the membrane upper surface has surface texturing.

As shown in FIGS. 8A and 8B, in the case where the membrane temperatureis estimated using the multiple linear regression equation, the estimatevalue of the membrane temperature can coincide with the actual measuredvalue of the membrane temperature by the thermocouple with extremelyhigh accuracy. By storing the calculated multiple regressioncoefficients in the polishing apparatus in advance, the membranetemperature can be estimated with high accuracy during the polishingprocess. Further, FIG. 8B shows the results in the case where theestimate values are calculated by the multiple linear regressionanalysis using the data of FIG. 7B in which surface texturing is appliedto the upper surface of the membrane. The estimate values of the case ofFIG. 8B can coincide with the actual measured values of the membranetemperature by the thermocouple with higher accuracy than those of thecase of FIG. 7B. Specifically, the multiple linear regression analysiswhich takes into account the carrier temperature is effective also inthe area where surface texturing is applied.

FIG. 9 is a graph showing the results in which the membrane temperaturesare estimated from the measured values of the infrared radiationthermometer and the measured values of the carrier temperature in FIG. 5by using the multiple linear regression equation. In FIG. 9, measurementis carried out at the area having no surface texturing. It is confirmedfrom FIG. 9 that although there are locations where the correctionvalues of the infrared radiation thermometer measurement which arecorrection values by liner approximation (simple linear regressionequation) in the case of FIG. 7A are different from the actual measuredvalues of the membrane temperature by the thermocouple, the estimatevalues of the membrane temperature obtained by using the multiple linearregression equation coincide with the actual measured values of themembrane temperature by the thermocouple with extremely high accuracy.

Next, a method for estimating wafer temperature (substrate temperature)using the estimate value of the membrane temperature will be describedbelow. FIG. 10 is a graph in which the estimate values of the membranetemperature calculated by the above membrane temperature estimateequation (2) are plotted on the horizontal axis and the measured valuesof the temperature of the wafer lower surface by the thermocouple at thesame time are plotted on the vertical axis using all time-series datashown in FIG. 5. FIG. 10 shows that the estimate values of the membranetemperature are lower than the actual measured values of wafertemperature by the thermocouple at the time of forced heating. Incontrast, the estimate values of the membrane temperature are higherthan the actual measured values of wafer temperature by the thermocoupleat the time of forced cooling. This phenomenon will be described below.

The membrane temperature is affected by both of the wafer temperatureand the carrier temperature from the standpoint of thermal balance. Themembrane temperature is lower than the wafer temperature by the effectof the low-temperature carrier at the time of forced heating. Incontrast, the membrane temperature is higher than the wafer temperatureby the effect of the high-temperature carrier at the time of forcedcooling.

In FIG. 10, the estimate values of the membrane temperature may bedetermined by the simple linear regression analysis of the equation (1),and the estimate values of the wafer temperature may be determined bythe simple linear regression analysis from the correction values of theinfrared radiation thermometer measurement. In this case also,especially in the case where surface texturing is applied to the uppersurface of the membrane, when the infrared light radiated from thecarrier is diffusely reflected from the upper surface of the membrane,the wafer temperature can be estimated with high accuracy. A certainlevel of estimation of the wafer temperature can be made by the simplelinear regression equation which uses the estimate values of themembrane temperature. In order to estimate the wafer temperature withhigher accuracy, the estimate value can be calculated with high accuracyby estimating the wafer temperature by the multiple linear regressionequation which uses the membrane temperature and the carriertemperature. In this multiple linear regression analysis also,regression coefficients b₀, b₁ and b₂ which minimize (the measured valueof the wafer temperature by the thermocouple−the estimate value of thewafer temperature)² are calculated. Specifically, the multiple linearregression analysis which uses a method of least squares is employed.(The estimate value of the wafer temperature)=b ₀ +b ₁×(the estimatevalue of the membrane temperature)+b ₂×(the measured value of thecarrier temperature)  equation (3)

FIG. 11 is a graph in which the estimate values of the wafer temperatureare plotted on the horizontal axis and the measured values of thetemperature of the wafer lower surface by the thermocouple at the sametime are plotted on the vertical axis in the case where regressioncoefficients b₀, b₁ and b₂ which minimize (the measured value of thewafer temperature by the thermocouple−the estimate value of the wafertemperature)² by the above equation (3) are calculated by application ofthe actual measured values. In the case where the wafer temperature isestimated using the multiple linear regression equation (3), theestimate values of the wafer temperature can coincide with the actualmeasured values of the temperature of the wafer lower surface by thethermocouple with extremely high accuracy.

FIG. 12 is a graph showing the results in which the wafer temperaturesare estimated using the multiple linear regression equation from themeasured values of the infrared radiation thermometer and the measuredvalues of the carrier temperature in the case of FIG. 5. It is confirmedthat the estimate values of the wafer temperature obtained by using themultiple linear regression equation coincide with the actual measuredvalues of the temperature of the wafer lower surface by the thermocouplewith extremely high accuracy. By storing the calculated multipleregression coefficients in the polishing apparatus in advance, the wafertemperature can be estimated with high accuracy during the polishingprocess. In a preliminary experiment for determining multiple regressioncoefficients as shown in FIG. 4, it is desirable that the pressurechamber is pressurized by the same pressure as that for actualpolishing. Further, in the case where the actual polishing (polishingperformed actually) is carried out under some pressure conditions,multiple regression coefficients may be calculated for each pressurecondition in advance, and the multiple regression coefficients may beselectively used in accordance with the pressure condition at the timeof actual polishing. In the present embodiment, the multiple linearregression analysis incorporating the carrier temperature as a typicaltemperature of the substrate holding apparatus (top ring) has beenperformed. In order to calculate the estimate value of the temperaturewith high accuracy, it is desirable to use the temperature of theportion of the carrier facing the membrane. However, the temperature ofother portions (member) of the substrate holding apparatus may be usedinstead of the carrier temperature. In this case, if the temperature ofthe member connected to the carrier is used, the estimate value of thetemperature can be calculated with relatively high accuracy.

FIG. 13 is a flow chart showing one aspect of a process for determiningpolishing conditions and the like by estimating the wafer temperature(substrate temperature) from the measured value of the infraredradiation thermometer and the measured value of the carrier temperatureperformed in the polishing apparatus according to the present invention.

As shown in FIG. 13, data acquisition and calculation of the estimateequation are carried out in advance. Specifically, as in the case ofFIG. 4, the temperature of the wafer lower surface is measured by thethermocouple 51, the temperature of the membrane upper surface ismeasured by the thermocouple 49, the infrared radiation temperature ismeasured by the infrared radiation thermometer 45, and the temperatureof the carrier is measured by the thermocouple 48. Next, the estimateequation is calculated using these measured values. In this case, theestimate equations in a plurality of pressure chambers are similarlycalculated as required. The measured value of the infrared radiationthermometer is compared with the measured value obtained by thecontact-type thermocouple, and a slope of the measured value of theinfrared radiation thermometer and a deviation between the measuredvalue of the infrared radiation thermometer and the measured valueobtained by the contact-type thermocouple are corrected. Then, theestimate equation of the membrane temperature is calculated by multiplelinear regression analysis which uses the correction values of theinfrared radiation thermometer measurement and the measured values ofthe carrier temperature. Then, the estimate equation of the wafertemperature is calculated by multiple linear regression analysis whichuses the estimate values of the membrane temperature and the measuredvalues of the carrier temperature. Thereafter, the calculated estimateequation of the wafer temperature is stored in the polishing apparatus.

At the time of actual polishing, the measured value of the infraredradiation thermometer and the measured value of the carrier temperaturemeasured at the time of polishing are substituted into the aboveestimate equation of the wafer temperature, and the estimate value ofthe wafer temperature at the time of polishing is calculated. Ifnecessary, the polishing conditions are changed using the calculatedestimate value of the wafer temperature at the time of polishing.

Next, a problem of dew condensation in the membrane which has beenexplained in Summary of the Invention will be described below. The dewcondensation in the membrane lowers accuracy of temperature measurementor destabilizes pressures applied to the wafer.

FIG. 14A is an enlarged view of XIV part of FIG. 2. As shown in FIG.14A, the valve V1-3 is capable of communicating with the atmosphere.When the passage communicating with the pressure chamber (for example,the central chamber) is switched from the vacuum state to the state ofthe pressure release to an atmospheric pressure, air in the atmospherein which the polishing apparatus is placed enters the passage from thevalve V1-3 to expose the pressure chamber to an atmospheric pressure. Atthis time, air containing water content enters the pressure chamber, anddew condensation occurs in the membrane by repetition of temperaturerise and temperature drop of the gas in the above pressure chamber. Thesame holds true for the valve V2-3 and the like corresponding to otherpressure chambers (for example, the ripple chamber 6). When dewcondensation occurs in the membrane of the pressure chamber to generatewater droplets on the upper surface of the membrane, a quantity of theinfrared light radiated from the portion having the water droplets isvaried in comparison with the case where there is no water droplets.Therefore, the membrane temperature cannot be measured with highaccuracy. Further, when an amount of water droplets caused by dewcondensation increases, water is accumulated in the pressure chamber tochange a pressure applied to the wafer (substrate), and thus stablepolishing cannot be carried out.

In order to prevent air containing water content from entering thepressure chamber, an atmospheric-pressure N₂ (dry gas) is supplied whena pressure in the pressure chamber increases from the vacuum state to anatmospheric pressure. Dry air containing no water content, other thanN₂, may be used. In this case, the dry air means a gas source whosedew-point temperature under atmospheric pressure is not more than 20° C.Deionized water (pure water) used for cleaning the top ring has atemperature of approximately 20° C., normally, and if a gas whosedew-point temperature is not more than 20° C. is used, dew condensationdoes not occur even if the gas is cooled down to approximately 20° C.The dry gas is preferably an inert gas.

FIG. 14B is a view showing a piping system for supplying N₂ having anatmospheric pressure into the pressure chamber. As shown in FIG. 14B,the valve V1-3 is connected via a regulator or a pressure controller 55to a pressurized N₂ source 56. The regulator or the pressure controller55 depressurizes a pressurized N₂ supplied from the pressurized N₂source 56 to an atmospheric pressure. In this manner, in order to supplyan atmospheric-pressure N₂ to the pressure chamber, the pressurized N₂may be depressurized to an atmospheric-pressure N₂ by the regulator(decompression valve) or the pressure controller. In contrast, when thepressure chamber is depressurized from the pressurized state to anatmospheric pressure, the valve V1-3 communicating with the pressurechamber is opened, and the pressurized gas is discharged from a reliefvalve of the regulator and is depressurized. Thus, air containing watercontent is prevented from entering the passage. Further, a container forstoring an atmospheric-pressure N₂ may be provided, and theatmospheric-pressure N₂ may be supplied from the container to thepressure chamber to heighten responsiveness upon change to theatmospheric pressure. According to the present invention, the passagecommunicating with the pressure chamber is connected only to the gassource isolated from the atmosphere in which the polishing apparatus isplaced. Specifically, because the passage communicating with thepressure chamber is constructed such that the passage is not connectedto the atmosphere in which the polishing apparatus is placed, watercontent in the air does not enter the passage to prevent dewcondensation from occurring in the pressure chamber.

Also, in the aspect in which a dry gas source is not provided as shownin FIG. 2, a water content removing device may be provided in thepassages (passages 21, 22, 23 and 24 or passages 11, 12, 13 and 14 inthe embodiment of FIG. 2) communicating with the pressure chamber inwhich the infrared radiation thermometer is installed, thereby supplyinga gas whose dew-point temperature is not more than 20° C. to eachpressure chamber. As the water content removing device, water-absorbingmaterial such as silica gel or water absorptive polymer is provided inthe passage, and the water-absorbing material is replaced with new onesimultaneously with replacement of the membrane or the like. As othermeans, in order to prevent dew condensation from occurring in thepressure chamber side, it is considered that the membrane itself isconstructed by a membrane having high thermal insulation or warm wateris used for cleaning the top ring, thereby preventing the temperature ofthe membrane from lowering.

Next, the data receiving unit 47 shown in FIG. 3 will be describedbelow. As shown in FIG. 3, the data receiving unit 47 is installed inthe top ring 1 which rotates during the polishing process, and thus itis necessary to transmit signals between a rotating part and astationary part for signal transmission between the controller of thepolishing apparatus and the data receiving unit 47. For this signaltransmission, a slip ring may be used or radio communication such aselectric wave communication or optical communication may be used (notshown). According to the present embodiment, signals measured by theinfrared radiation thermometer 45 or the thermocouple 48 are convertedinto digital signals by the analog-to-digital converter of the coldjunction temperature sensor unit 46, and the digital signals aretransmitted to the data receiving unit 47. Then, the digital signals aretransmitted from the data receiving unit 47 to the controller 50 of thepolishing apparatus (see FIG. 1), and thus this system is insusceptibleto noise caused by the slip ring or the radio communication. A slip ringmay be used for power supply to the data receiving unit 47, ornoncontact power supply to the data receiving unit 47 may be performedusing coils or the like. Further, a rechargeable battery may be providedin the top ring 1 to supply power. In this case, the remaining batterylevel may be recognized by the controller 50 of the polishing apparatus,and an alarm for notifying replacement of the battery when the remainingbattery level is low may be issued from the polishing apparatus.

Next, a method of controlling the temperature of the pressure chamberwill be described. FIG. 15 is a schematic cross-sectional view of thetop ring having structure for performing the temperature control of thepressure chamber. In FIG. 15, the infrared radiation thermometers andsome elements illustrated in FIG. 3 are omitted. As shown in FIG. 15, afirst pressure controller 60-1 and a second pressure controller 60-2 arecoupled to one pressure chamber (e.g., the central chamber 5). Apressure sensor 61 for monitoring the pressure in the pressure chamber(the central chamber 5) is provided. The two pressure controllers 60-1and 60-2 are set to the same control pressure at the start of polishing.When the estimate value of the wafer temperature exceeds a predeterminedtemperature during the polishing process, the set value of one of thepressure controllers 60-1 and 60-2 is lowered. For example, at the startof polishing, both of the pressure controller 60-1 and the pressurecontroller 60-2 pressurize a fluid at a set value of 200 hPa. Duringpressurizing, the wafer is pressed at 200 hPa. When the estimate valueof the wafer temperature exceeds the predetermined temperature, the setpressure of the pressure controller 60-2 is lowered to 180 hPa, whilethe set pressure of the pressure controller 60-1 is maintained at 200hPa. In this case, the pressurized fluid flows from a fluid passagecommunicating with the pressure controller 60-1 toward a fluid passagecommunicating with the pressure controller 60-2. This flow of thepressurized fluid cools the interior of the pressure chamber (thecentral chamber 5). Further, during cooling, the pressure in thepressure chamber is monitored by the pressure sensor 61. When thepressure in the pressure chamber drops far below 200 hPa, the setpressure of the pressure controller 60-2 is increased so that a desiredpressure is developed in the pressure chamber.

In order to further improve a cooling effect in the pressure chamber, itis preferable to further lower the set pressure of the pressurecontroller 60-2 so as to increase a flow rate of the pressurized fluidflowing through the pressure chamber. The pressurized fluid may have acontrolled temperature. For example, the pressurized fluid having a lowtemperature may be used to further improve the cooling effect.Alternatively, the pressurized fluid having a high temperature may beused. For example, when the estimate value of the wafer temperature isnot more than the predetermined temperature, the high-temperaturepressurized fluid may be passed through the pressure chamber so as toincrease the temperature of the wafer. It is also possible to use acombination of the low-temperature pressurized fluid and thehigh-temperature pressurized fluid. For example, when the temperature ofthe wafer is low at the initial stage of polishing, the high-temperaturepressurized fluid is passed through the pressure chamber so as toaccelerate the increase in the temperature of the wafer, and when thetemperature of the wafer becomes high during polishing, the pressurizedfluid having a low temperature or an ordinary temperature is passedthrough the pressure chamber so as to suppress the increase in thetemperature of the wafer. The membrane for pressing the wafer may beconfigured to define a plurality of pressure chambers, and the wafertemperature may be estimated and controlled in the respective pressurechambers. Alternatively, the wafer temperature may be estimated in oneof the pressure chambers and the temperature control may be performedusing this estimated temperature. Further, since the pressure sensor 61has a temperature characteristic, the measured value of the pressuresensor 61 may be compensated using the temperature measurement result ofthe carrier 43.

The estimate value of the wafer temperature is further used for changingvarious polishing conditions. When the estimate value of the wafertemperature of a portion corresponding to one pressure chamber (e.g.,the central chamber 5) is higher than the estimate value of the wafertemperature of a portion corresponding to another pressure chamber(e.g., the ripple chamber 6) during polishing, the pressure of the onepressure chamber (the central chamber 5) is lowered so as to suppressthe increase in the temperature, or the pressure of another pressurechamber (the ripple chamber 6) is increased so as to accelerate theincrease in the temperature of that pressure chamber (the ripple chamber6). Further, a cooling and heating device for the polishing surface 101a (see FIG. 1), which is provided outside the substrate holdingapparatus, may be used for controlling the temperature of the polishingsurface 101 a in its entirety or may be used for controlling atemperature of a portion of the polishing surface 101 a corresponding tothe pressure chamber whose temperature is measured. Examples of thetemperature controlling device for the polishing surface include adevice configured to bring a medium into contact with the polishingsurface so as to control the temperature thereof and a device configuredto blow a fluid onto the polishing surface. In order to control thepolishing temperature, the pressing force of the retainer ring 3 (seeFIG. 1) may be changed, or the dressing conditions, such as a dressingload and a scanning speed, may be changed in a portion of the polishingsurface corresponding to the pressure chamber whose temperature ismeasured so as to accelerate or suppress the polishing process. Thedressing conditions may be changed when performing In-situ dressing(which is a dressing operation performed during polishing) or Ex-situdressing (which is a dressing operation performed after polishing). Theflow rate of the polishing slurry may be changed for the temperaturecontrol, and a dropping position of the polishing slurry may be changedusing the temperature measurement results. The combination of thesetemperature controlling devices may also be used. Further, thetemperature of the polishing surface may be measured, and theabove-described temperature control may be performed using thetemperature measurement result of the polishing surface and thetemperature measurement result of the wafer.

Next, specific examples of the aforementioned temperature controllingdevice for the polishing surface will be described with reference toFIGS. 16 through 21.

FIG. 16 is a schematic plan view showing an arrangement of the polishingliquid supply nozzle for supplying the polishing slurry (polishingliquid), the polishing pad, and the top ring. As shown in FIG. 16, thepolishing liquid supply nozzle 102 is provided above the polishing table100, so that the polishing liquid supply nozzle 102 drops (or supplies)the polishing slurry onto a predetermined position of the polishing pad101 on the polishing table 100. A tip of a nozzle portion of thepolishing liquid supply nozzle 102 is adjacent to the top ring 1.

FIG. 17 is a schematic plan view showing an example of the temperaturecontrolling device for the polishing pad. In the example shown in FIG.17, when the wafer has a high temperature, a polishing pad temperaturecontrolling device 70, which has been cooled by a cooling medium, isbrought into contact with the polishing pad 101 to thereby cool thepolishing pad (i.e., the polishing surface).

FIG. 18 is a schematic plan view showing another example of thetemperature controlling device for the polishing pad. In the exampleshown in FIG. 18, the polishing pad temperature controlling device 70strongly cools a portion of the polishing pad 70 that lies in a positioncorresponding to a high-temperature portion of the wafer (e.g., thecentral portion of the wafer). Specifically, stronger cooling isperformed by a central portion of the polishing pad temperaturecontrolling device 70 for cooling the portion of the polishing padcorresponding to the central portion of the wafer. Simultaneously,weaker cooling is performed by both side portions of the polishing padtemperature controlling device 70 for cooling a portion of the polishingpad corresponding to other portion of the wafer, or that portion of thepolishing pad is not cooled or is heated.

FIG. 19 is a schematic plan view showing an example in which thedressing load (dress load) and/or the scanning speed is changed. Asshown in FIG. 19, a disk-shaped dresser 80 for dressing the polishingpad 101 on the polishing table 100 is provided. During dressing, thedresser 80 is pressed against the polishing pad 101 at a predetermineddressing load. Further, the dresser 80 can be oscillated within adresser scanning range by a horizontally-extending oscillation shaft 81.When the temperature of the central portion of the wafer is high (orlow), the dressing load for dressing a portion of the polishing pad thatlies in a position corresponding to the high-temperature portion (orlow-temperature portion) of the wafer is reduced (or increased) tothereby adjust the polishing performance of the polishing pad. When thetemperature of the central portion of the wafer is high (or low), thescanning speed for dressing a portion of the polishing pad that lies ina position corresponding to the high-temperature portion (orlow-temperature portion) of the wafer is reduced (or increased) tothereby adjust the polishing performance of the polishing pad. Thedressing conditions may be changed when performing the In-situ dressingwhich is a dressing process performed during polishing, or may bechanged when performing the Ex-situ dressing which is a dressing processperformed after polishing.

FIG. 20 is a schematic plan view showing an example of changing thedropping position of the polishing slurry in accordance with thetemperature of the wafer. As shown in FIG. 20, when the temperature ofthe central portion of the wafer is high, an angle of the polishingliquid supply nozzle 102 is changed, so that the dropping position ofthe polishing slurry lies on a trajectory (Lc) of the wafer centerdescribed on the polishing pad.

FIG. 21 is a schematic plan view showing an example in which thetemperature (distribution) of the polishing pad surface is measuredsimultaneously with the wafer temperature measurement and thetemperature control is performed based on the measurement results. Inthe example shown in FIG. 21, a plurality of infrared radiationthermometers 82 are provided above the polishing table 100. Theseinfrared radiation thermometers 82 are located away from the polishingpad 101 on the polishing table 100. The temperature of the polishingsurface of the polishing pad 101 is measured by the plurality ofinfrared radiation thermometers 82, whereby a temperature distributionof the polishing pad surface is measured. Then, the temperature controlof the wafer is performed using the estimation result of the wafertemperature and the measurement result of the polishing surfacetemperature.

Other than the embodiments shown in FIG. 16 through FIG. 21, thepolishing conditions may be changed using a combination of the estimatevalue of the wafer temperature (i.e., the estimate value of thesubstrate temperature) and information obtained by a sensor (e.g., anoptical type or an eddy current type) that is embedded in the polishingtable and is configured to measure a surface, being polished, of thewafer. For example, when time variation in the film thickness monitoredby the eddy current sensor is slower in the central portion of the waferthan in other area during polishing and when the estimate value of thetemperature is high in the central portion of the wafer, the temperaturecontrolling device is controlled so as to lower the temperature of thecentral portion of the wafer. This is a case of process in whichpolishing is suppressed when the temperature rises above a certainvalue. It is possible to combine various types of control methods inaccordance with processes. It is preferable that no opening (e.g., hole)exists in the wafer contact surface of the membrane that defines thepressure chamber in which the membrane temperature is measured. This isbecause a hole permits a cleaning liquid to enter the upper surface sideof the membrane during a cleaning operation of the substrate holdingapparatus and such a cleaning liquid could lower the accuracy of themembrane temperature measurement. In a case of providing an opening(e.g., a hole), it is preferable to eject a gas, such as N₂, from thecarrier side onto the membrane temperature measuring zone during thecleaning operation of the substrate holding apparatus so as to removewater droplets.

In the case of using the substrate holding apparatus having theplurality of pressure chambers, the plurality of temperature sensors(e.g., the infrared radiation thermometers) for measuring thetemperature of the membrane are provided so as to correspond to all ofthe pressure chambers and one measuring device is provided for measuringthe carrier temperature, so that the wafer temperatures at positionscorresponding to the respective pressure chambers can be estimated bythe multiple linear regression equations provided for the respectivemembrane temperature sensors. Instead of providing the temperaturesensors for all of the pressure chambers, at least two membranetemperature sensors may be provided. In this case, the measurementresults of the at least two sensors may be used to interpolate andestimate the wafer temperature at a position corresponding to thepressure chamber with no membrane temperature sensor provided. The wafertemperature may be estimated from the measurement results of the twomembrane temperature sensors using linear interpolation or otherinterpolation such as quadratic. According to this approach, thetemperature distribution over the wafer surface can be estimated usingless membrane temperature sensors. Further, the polishing conditions maybe changed using the estimate temperature of the pressure chamber whereno membrane temperature sensor is provided. For example, when theestimate temperature of the pressure chamber is high, the pressure inthat pressure chamber is lowered.

FIG. 22 is a cross-sectional view showing more detailed structures ofthe top ring having the infrared radiation thermometer and thethermocouple for measuring the carrier temperature.

The top ring 1 shown in FIG. 22 corresponds to the top ring 1 shown inFIG. 3 with more detailed structures. As shown in FIG. 22, the top ring1 is basically constituted by the top ring body 2 configured to pressthe semiconductor wafer against the polishing surface 101 a (see FIG. 1)and the retainer ring 3 configured to press the polishing surface 101 adirectly. The top ring body 2 includes the disk-shaped top ring flange41, the top ring spacer 42 attached to a lower surface of the top ringflange 41, and the carrier 43 attached to a lower surface of the topring spacer 42. The retainer ring 3 is attached to the peripheralportion of the top ring flange 41 of the top ring body 2. The top ringflange 41 is coupled to the top ring shaft 111 by bolts 308. The topring spacer 42 is secured to the top ring flange 41 by bolts (notshown), and the carrier 43 is secured to the top ring spacer 42 by bolts(not shown). The top ring flange 41, the top ring spacer 42, and thecarrier 43 constitute the top ring body 2, which is made of resin, suchas engineering plastic (e.g., PEEK). The top ring flange 41 may be madeof metal, such as SUS or aluminum.

The elastic membrane 4 that is brought into contact with the rearsurface of the semiconductor wafer is attached to the lower surface ofthe carrier 43. More specifically, the membrane 4 is attached to thelower surface of the carrier 43 by an annular edge holder 316 disposedat the peripheral portion of the membrane 4 and annular ripple holders318 and 319 disposed inwardly of the edge holder 316. The membrane 4 ismade of rubber material having excellent strength and durability, suchas ethylene propylene rubber (EPDM), polyurethane rubber, and siliconerubber.

The edge holder 316 is held by the ripple holder 318, which is attachedto the lower surface of the carrier 43 by a plurality of stoppers 320.Similarly, the ripple holder 319 is attached to the lower surface of thecarrier 43 by a plurality of stoppers (not shown). The central chamber 5is formed on the central portion of the membrane 4.

The ripple holder 318 is arranged so as to press a ripple 314 b of themembrane 4 against the lower surface of the carrier 43, and the rippleholder 319 is arranged so as to press a ripple 314 a of the membrane 4against the lower surface of the carrier 43. An edge 314 c of themembrane 4 is pressed against the edge holder 316 by the ripple holder318.

The central chamber 5 is formed on the central portion of the membrane4. Further, the annular ripple chamber 6 is formed between the ripple314 a and the ripple 314 b of the membrane 4. The annular outer chamber7 is formed by the outer partition wall 314 b and the edge partitionwall 314 c of the membrane 4. The annular edge chamber 8 is formed bythe edge partition wall 314 c and a side wall 314 e of the membrane 4.The pressure chambers 5, 6, 7, and 8 are connected to the pressureregulating unit 30 (see FIG. 2) via fluid passages formed in the topring body 2.

The retainer ring 3 is configured to hold a peripheral edge of thesemiconductor wafer. This retainer ring 3 includes a cylinder 400 havinga closed top portion, a holding member 402 secured to the top portion ofthe cylinder 400, a membrane 404 held in the cylinder 400 by the holdingmember 402, a piston 406 connected to a lower end portion of themembrane 404, and a ring member 408 which is pushed down by the piston406. The retainer ring pressure chamber 9 is formed in the membrane 404.This membrane 404 is made of rubber material having excellent strengthand durability, such as ethylene propylene rubber (EPDM), polyurethanerubber, and silicone rubber.

The holding member 402 is provided with a fluid passage (not shown)communicating with the retainer ring pressure chamber 9 defined by themembrane 404. This fluid passage formed in the holding member 402 isconnected to the pressure regulating unit 30 (see FIG. 2) via a fluidpassage formed in the top ring body 2.

In the top ring 1 according to this embodiment, the pressures of thefluid supplied to the pressure chambers formed between the membrane 4and the carrier 43 (i.e., the central chamber 5, the ripple chamber 6,the outer chamber 7, and the edge chamber 8) and the pressure of thefluid supplied to the retainer ring pressure chamber 9 can be adjustedindependently. According to such structures, the pressing force of themembrane 4 that presses the semiconductor wafer against the polishingpad 101 can be adjusted in each area of the semiconductor wafer, and thepressing force of the retainer ring 3 that presses the polishing pad 101can be adjusted as desired.

In the embodiment shown in FIG. 22, the infrared radiation thermometer45 faces the central chamber 5 of the membrane 4. This infraredradiation thermometer 45 may be arranged so as to face another pressurechamber. In such a case, a position of the partition wall of thepressure chamber with respect to a radial direction of the wafer may bemodified appropriately. In order to minimize an influence of noise, theinfrared radiation thermometer 45 is located near the membrane 4 andarranged so as to face the membrane 4 (i.e., located at the carrierside). An O-ring 85 is provided between an outer surface of the infraredradiation thermometer 45 and the carrier 43, so that the pressurizedfluid and vacuum pressure in the pressure chamber do not leak. Thethermocouple 48 for measuring the temperature of the carrier 43 isprovided on the upper surface of the carrier 43 and arranged in aposition corresponding to the central chamber 5. A plurality ofthermocouples 48 for measuring the temperature of the carrier 43 may beprovided on the upper surface of the carrier 43 so as to correspond tothe respective pressure chambers. A measured value obtained from one ofthe thermocouples 48 may be used as a temperature representing thetemperature of the carrier 43. The temperature of the lower surface ofthe carrier 43 may be measured directly. In the case of measuring thetemperature of the lower surface of the carrier 43 by the thermocoupleon the upper surface of the carrier 43, it is preferable to make thecarrier 43 as thin as possible in order to enable the thermocouple tomeasure the temperature of the lower surface of the carrier 43 with agood responsiveness. Further, since the carrier 43 is a removablecomponent that is removed when replacing consumables of the top ring, itis preferable to use thermocouple connectors for connecting wires fromthe infrared radiation thermometer and the thermocouple in order toprovide an easily removable structure.

In the top ring 1 constructed as shown in FIG. 22, the infraredradiation thermometer 45 measures a quantity of the infrared lightradiated from the membrane 4, the thermocouple 48 measures thetemperature of the carrier 43, and the wafer temperature is estimatedfrom the measured value of the infrared radiation thermometer 45 and themeasured value of the thermocouple 48, as discussed previously withreference to FIGS. 3 through 13.

Although the embodiments of the present invention have been describedherein, the present invention is not intended to be limited to theseembodiments. Therefore, it should be noted that the present inventionmay be applied to other various embodiments within a scope of thetechnical concept of the present invention.

What is claimed is:
 1. A polishing apparatus for polishing a substrate,comprising: a polishing table having a polishing surface; a substrateholding apparatus configured to hold the substrate and to press thesubstrate against said polishing surface; and a controller; saidsubstrate holding apparatus comprising: an elastic membrane configuredto form a substrate holding surface which is brought into contact withthe substrate; a carrier provided above said elastic membrane; at leastone pressure chamber formed between said elastic membrane and saidcarrier; and an infrared light detector configured to measure thermalenergy from said elastic membrane; wherein said controller calculates anestimate value of a temperature of said elastic membrane using ameasured value of said infrared light detector.
 2. A polishing apparatusaccording to claim 1, wherein said controller calculates an estimatevalue of a temperature of the substrate using the estimate value of thetemperature of said elastic membrane.
 3. A polishing apparatus accordingto claim 1, wherein a polishing condition is changed using the estimatevalue of the temperature of said elastic membrane.
 4. A polishingapparatus according to claim 1, wherein said infrared light detectorcomprises an infrared radiation thermometer.
 5. A substrate holdingapparatus for holding a substrate and pressing the substrate against apolishing surface, comprising: an elastic membrane configured to form asubstrate holding surface which is brought into contact with thesubstrate; a carrier provided above said elastic membrane; at least onepressure chamber formed between said elastic membrane and said carrier;and an infrared light detector configured to measure thermal energy fromsaid elastic membrane; wherein surface roughing processing is applied toa rear surface side of said substrate holding surface of said elasticmembrane.
 6. A substrate holding apparatus according to claim 5, whereinat least two pressure chambers are formed between said elastic membraneand said carrier, and said infrared light detector is provided in atleast one pressure chamber of said at least two pressure chambers.
 7. Asubstrate holding apparatus according to claim 5, wherein said substrateholding surface of said elastic membrane for forming said pressurechamber in which said infrared light detector is provided has noopening.
 8. A substrate holding apparatus according to claim 5, whereinsaid infrared light detector comprises an infrared radiationthermometer.
 9. A polishing apparatus comprising: a polishing tablehaving a polishing surface; and a substrate holding apparatus forholding a substrate and pressing the substrate against a polishingsurface, comprising: an elastic membrane configured to form a substrateholding surface which is brought into contact with the substrate; acarrier provided above said elastic membrane; at least one pressurechamber formed between said elastic membrane and said carrier; and aninfrared light detector configured to measure thermal energy from saidelastic membrane; wherein surface roughing processing is applied to arear surface side of said substrate holding surface of said elasticmembrane.